MacBook Pro display weirdness

I own a shiny new-model macbook pro, which I delight in very much. However, a couple of months ago I came across an initially very alarming problem which turned out to have a simple fix. I've finally got round to blogging about it in case anybody else should witness the same behaviour.

Now, much as I love Apple's hardware and software, I sometimes find their decisions a bit arbitrary and annoying. For instance, they removed a perfectly good DVI port from their macbook pros and replaced it with the new mini-display-port thingy. This means I had to buy two adapters -- one for DVI monitors and another for good ol' VGA. Anyway, that is by-the-by. This story is about what happened when I connected a "big telly" to this preposterously tiny port on a fine day last August.

I did this as I wanted to watch a DVD (the most excellent Lives of Others, since you ask). This procedure went well. When finished, I pulled out the displayport adapter. At this point, I noticed that the display did its usual flicker thing, but seemed to go a bit more distorted than usual. But it came back to life after a short pause and I thought no more about it.

Until, that is, some days later when I came to restart the machine. It wouldn't boot up. Well, to be exact, it would boot up but only up to the point of the GUI appearing on screen. I'd get a brief ghostly flash of the desktop as it had been when the telly had been connected, and then the display would either turn all-blue, or (more frequently) show what I can only describe as coloured static. You know white noise on a (non-digital) telly? Well, my macbook was showing something like that, only instead of being black and white it was multicoloured, and it didn't move around like TV white noise. It was static static, if you like.

No key presses or mouse clicks seemed to have any effect. The only thing I could do was perform a hard restart. Which I did, several times. But the exact same thing happened every time.

So I started in safe mode and -- much to my relief, as it meant a hardware problem was less likely -- the machine started normally. However, restarting in normal mode meant more coloured static. I tried a Snow Leopard reinstall (the quick type, where it reinstalls the OS but doesn't reformat the disk or anything). No joy. By this time I was beginning to think a full reinstall from scratch might be needed. And I was becoming a bit concerned that perhaps the faster of the macbook's two graphics chips was actually faulty.

The interwebs were no real help, but after a bit of reading up around the mac windowing technology I wondered if perhaps getting rid of a corrupt plist file might help. So, crossing fingers and toes, I ssh'd into the coloured static machine and deleted:

/Library/Preferences/com.apple.windowserver.plist

and

~/Library/Preferences/ByHost/com.apple.windowserver.[HEXNUMBER].plist

(where [HEXNUMBER] varies depending on your own profile).

One restart later and -- with immense relief -- my display was back in action. Phew.

A couple of weeks later, I noticed Apple issued an update for Macbook Pros which amongst other things addressed "problems when connecting external displays" so hopefully I will never see this error again. And hopefully neither will you. But just in case...